Police dove out of the way and the Mercedes dragged the other suspect's body down the block.

A doctor involved in treating the dead suspect says he had injuries head to toe and all limbs intact when he arrived at the hospital. After 15 minutes of unsuccessful treatment, doctors pronounced him dead.

The older Tsarnaev's clothes had been cut off by emergency responders at the scene, so if he had been wearing a vest with explosives, he wasn't by the time he arrived at the hospital, the doctor said.

An official motive for the marathon bombing attack is still unknown. But the FBI said a foreign government told it in early 2011 about information that Dzhokhar Tsarnaev's older brother, Tamerlan Tsarnaev, was a follower of radical Islam.

According to the FBI, the foreign government said Tamerlan Tsarnaev had changed drastically since 2010 as he prepared to leave the United States to join unspecified underground groups. The FBI says it interviewed him and relatives and didn't find any terrorism activity.

Over the last few days, officials have been examining clues about the suspects' background. The Tsarnaev's are ethnic Chechens who lived in the Dagestan region of southern Russia.

CBN News has reported on the growth of radical Islam in this region of the world. Click here for the report.

The younger Tsarnaev was finally found late Friday evening after authorities lifted a lock-down on the Boston Metro area.

Watertown resident Warren Tolman went outside after that and noticed something different with his boat in his backyard. He lifted the tarp covering it and found Tsarnaev.

"It's unbelievable, I was cooped up in my house for almost the last 24 hours wondering if the guy was in my backyard, if he was in my garage or in my neighborhood."

Much to his surprise that was the case. Tolman found Tsarnaev bloody, wounded, and weak from his gun battle.

So weak, agents and officers say, that they haven't been able to question him.

Police announced via Twitter that Tsarnaev was in custody: "CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody."

Residents, who've been on edge all week, say it was the news they'd been waiting to hear.

"It brings a sigh of relief and I think that it really allows us to start the healing process," said Watertown's Heather Budda.

Just blocks away from the bombing sites, students from Boston University gathered after hearing the news.

Wrapped in an American flag, BU student Aaron Wengertsman said, "I'm glad they caught him alive."

Others in Boston and beyond, took to the streets to celebrate. They chanted, "USA! USA!"